Spark plug



my 7, W53@ G. M. PAULSON MMWR v SPARK'PLUG Filed Sept. 14, 1935 Z2 Vj INVENTOR ATTORNEY Patented July 7, 1936 SPARK PLUG George M. Paulson, New York, N. Y., assignor to The B. G. Corporation, New York, N. Y., a corporatiol of New York Application september 14,' 193s, serial No. 689,338

' 5 claims. (ci. 12s-169) This invention relates to spark-plugs and their ignition leads or conductors, and more especially to spark-plugs which are shielded.against lWeather and oil and which together with their leads, are

l shielded against radio interference. The improvements constituting this invention are particularly applicable to aviation spark-plugs.

I'he insulated ignition leads usually lie more or less at right angles to the spark-plugs to which this, combined with the heating from the engine, develops deterioration which frequently results in electrical break-down.

The objects oi this invention are to provide a simple and advantageous means for protecting the ignition lead of a spark-plug both mechanically and 'against the eiect of heat, also to provide weather-tight connections and electrical bonding connections between the metal harness of the lead and the spark-plug.

Spark-plugs have been provided with various forms of hoods or shields into which the lead has been brought laterally. Insuch devices the insulated lead is brought in straight, without bending the insulation, provision being made within the hood to establish electrical connection between the wire and the spindle oi the plug.

Specifically, the present invention comprises 30 a combination or a particular type of radioshielded spark-plug, a curved, tubular, metal elbow, which forms part of the complete sparkplug, and connections at the two ends of the elbow adapted to make weather-tight joints with the spark-plug and with the lead and electrical bonds withV the harness and with the grounded part of the plug. The spark-plug is one in which a metal barrel, united or connected with the grounded shell o1 the spark-plug, extends upward above the spindle of the plug to provide a socket, which is lined with insulation. 'I'he insulated lead passes through the tubular metal elbow, which, therefore, requires no other internal insulation, and down into the socket of the spark-plug, where the end of. the lead is provided with a suitable terminal whichautomatically makes electrical contact with the spindle when the lead is inserted into the socket and the connection between the elbow and the spark-plug is made fast. One of the 50 connections grips or clasps the insulated lead so that it can not slip, and the connection between the elbow and the spark-plug constitutes a swivel which makes it possible to dispose the elbow in any position.

they are connected. The bending of the lead places a mechanical strain on the insulation, and p -tension current to the spindle.

` In the accompanying drawing:

Fig. 1 is a longitudinal section illustrating an embodiment of the invention; and Fig. 2 is a view on a smaller scale, partly in section and partly in elevation, showing some of the elements of a 5 diierent form.

The details of the spark-plugv may be varied. In the illustrated construction, the shell 2 is of conventional form, as is also the nut or bushing 3 screwed into the shell against a.v washer 4. A V10 spindle 5 surrounded by rolled lmica insulation 6 and having a head I and an electrode 8, of conventional form, is gripped in the body of the plug so as to produce a gas-tight joint, in a known manner, by forcing a compressible metal ring 9 15 upward in a tapered opening of the nut. As is also customary, mica disc insulation I0 is confined between this ring and the head. v

.The metal body of theplug is provided with a barrel II, which extends upward considerably above the upper end of the spindle to enclose the spindlel and the electrical'connection between the same and the conductor which leads the high- This barrel is preferably in one piece with the nut, though that is not necessary in all cases.

The hollow interior of the barrel is of considerably larger diameter than thek spindle and its insulating sleeve 6, and the barrel is lined throughout its length with a rolled mica sleeve I2, which is inserted from the upper end of the barrel. 1

The space in the lower part of the barrel between the mica sleeves 6 and I2 is occupied by a stack I5 ofI mica washers, this stack bearing at its lower end against a metal washer I6, which in vturn bears on a shoulder I1 of the body. A thin cup I8 and a heavy metal washer I9 overlie the mica disc insulation, and the upper end of the spindle 5 passes through these parts and is upset at 20 to secure the cup in place and to conne 40 the mica disc insulation under more or less compression.

The insulated conductor or lead I3 is passed through a tubular, curved, metal elbow 2|, which has a swiveled, detachable connection with the barrel Il. A continuous braided metal sheath or harness 22 covers all of the cable up to the elbow, to which it is connected. The manner of securing the elbow to the insulated conductor and electrically connecting it to the metal sheath may be varied. In the construction illustrated in Fig.

1, the outer end of the elbow has a screw-threaded enlargement 23, formed with a tapered mouth in which a conical rubber washer 24 is seated. A flanged collar 25 is soldered to the end oi the 55 sheath -2l and bears against the washer 24, and a coupling nut 26 screws on the enlargement 23 to draw the collar against the washer and squeeze the latter against its tapered seat and inward to clasp the insulation of the conductor.

The inner end oi the elbow 2l is soldered or otherwise secured in the narrow upper end ci a swivel coupling 2l designed for mechanical and electrical connection and disconnection with reference to the ban-ei il. The lower part oi this detachable connection is large enough to bass over the barrel for a distance limited by an internal shoulder 2S abutting the end oi the barrel.

The particular manner in which the elbow is connected to the spark-plug may be varied. lin

Fig. i, the lower part ci the detachable connection is slotted longitudinally to form numerous resilient ngers 2S to clasp the barrel. The latter has an external circumferential shoulder or.

y the ring is forced downward so that the humps seat in lthis groove, the lnbent portions Si are positively locked with the shoulder lili, so that the connection can not be pulled on the barrel as long as the ring is in this position.

ln Fig. 2, the construction of the spark-plug proper will be understood to be substantially sirnilar to that described in connection with Fig. l. Fig'.12 illustrates dierent forros of connections. It'also shows that the lead may have a fabric covering i563 over the metal harness 22, in which event the lead is prepared by cutting the covering o@ back a considerable distance from the end oi the wire and cutting the metal shielding 2li baci; a somewhat shorter distance,1

The outer end oi the elbow ille enters and is rmly secured to a nipple which is screwthreaded on the outside to receive a coupling nut 52, and the inside of which is formed with a tapering recess lili. cut-back end oi' the metallic braiding 22 is turned back over a tapered wedge ring 5d, which is forced by the nut 52 into the tapered recess, thereby strongly gripping the metal braiding to the metal nipple, forniing a tight joint and likewise holding the lead so thatit cannot pull out.

The connection between the inner end of theA elbowand the barrel il comprises a thimble 2l ilxed to theelbow and a coupling nut si, which screws onto the outside oi' the barrel and draws the member 2l against the end of the barrel, forming atight joint anda good electrical bond. Since the parts 2l and 2lb can be turned in relation to each other, the connection may be said to be of a swivel nature; that is to say, the elbow can be disposed in any angular relation to the spark-plug.

A length'of the insulated conductor i3 projects below. the connection member 2l cr 21 to enter the socket of the barrel, lined by the mica sleeve i2. 'I'hlsportion of the/ conductor carries and is surrounded by a tube of insulating material, for examplela rolled mica tube 5l, the opposite ends of which are bound by fer-rules '36 and 3l, similar to the fer-rule which binds the upper end of the lining sleeve I2.

This insulating tube acts as a spacer to prevent the conductor being pulled out of the sparkf plug when the connection 21 is in place. The upper endo! the tube, protected by the ferrule 36 bears against an internal -shoulder 38 of said 5l connection, whilst the i'errule Il is connected with the stranded wire 3! o1' the conductor.

The ferrule 3l may be formed with an internal web Ill having a central opening. The strands oi the conductor are passed through this opening and bent outward, and a headed screw or pin fastening el is inserted upward through the hole into the body of the conductor, where it spreads and rmly engages the strands or the conductor wire, laterally compressing the insulation di oi the conductor.

The head ol the fastening il also serves to secure to the end oi' the conductor the upper, small convolution ci a conical contact spring llt, which latter makes a sure electrical connection with the spindle 5 when the conductor is pushed into the barrel. The cup l, or the washer it, which may be regarded as part of the cup, forms a seat and an. electrical contact for the base ci this spring.

From the foregoing, it will be perceived that the 2li elbow is of a simple and inexpensive character, that electrical breakdown resulting from bending and overheating oi the insulation of the conductor or lead is avoided, that the connection at one end of the elbow holds the lead and forms a weathertight joint, and also an electrical bond with the harness of the lead, that electrical connection between the conductor wire and the spindle oi 'the spark-plug is made by inserting the projecting end oi the lead into the socket ol the spark-plug 3 lill ' and by securing to the plug the connection atthis end of the elbow, and that this connection formsv a weather-tight joint and an electrical bond with the grounded part oi the spark-plug, and also adorais a swivel. ln a shielded spark-plug of the f general character illustrated, the insulation of the portion of the lead inside the barrel or socket of the spark-.nlug is particularly subject to heating, because of the heat @owing through the metal of the spark-plug from the inner end oi the plug, which is exposed to the .high temperatures in the engine. In this invention, the elbow has a metal to metal connection with the barrel il, and provides additional cooling surface on the metal ci the plug. It results from this that the spark-plug is kept at e. lower. temperature than it would be without the elbow, and this aids materially in saving the insulation ci the lead inside the barrel of the plug from breakdown due to heat. Thus,

the elbow of thespark-olug serves several puiposes. It protects the insulation of the lead from too severe heating, as well as protecting this insulation from mechanical strain. It also forms ,cart oi' the complete electrical shielding of the spark-plug and its lead, and it likewise forms part 60 of the weather shielding ol' the plug.

This application ls acontinuation in part of application Serial No. 479,684, tiled September 4, 1930` (now Patent No. 1,930,322, dated Oct. 10, i933).

I claim:

l. An elbow spark-plug, comprising a sparkplug having a body or grounded portion provided with a socket lined with insulation and extending above the spindle o! the plus. a curved,.i tubular, metal elbow through which the insulated ignition lead extends to enter said socket, a detachable connection between the inner end ci.' said elbow and the top of the grounded portion of the spark-plug. and means gripping the lead at i6 the outer end oi the elbow and forming a weathertight entrance to the elbow.

2. An elbow spark-plug, comprising a sparkplug having a. body or grounded portion provided with a socket lined with insulation and extending above the spindle oi the plug, a curved, tubu lar, metal elbow through which the insulation ignition lead extends to enter said socket, a de tachable connection between the inner end of said elbowv and the top of the grounded portion of the spark-plug, and a connection at the outer end of the elbow adapted to retain the insulated lead and to be electrically bonded to a metal harness.

`3. The combination of a spark-plug having a spindle and a body or grounded portion provided' with a metal barrel which extends above the spindie to provide a socket, an insulated lead provided with a metal harness for radio shielding, a curved, tubular, metal elbow through which the lead with its insulation is passed, the end ot the insulated lead projecting below the elbow and being' provided with a terminal adapted to make electrical connection with the spindle, a connection at the outer end of the elbow forming` a weather-tight stantial wall thickness providing a conduit for the lead immediately above the socket and adapted to be connected at its upper end with a metallic shielding of the insulated lead, and a metal to metal connection between the elbow and said bar- 5 rel, said elbow providing additional cooling surI face on the metal of the spark-plug and thereby protecting the insulation 'of the lead inside the spark-plug from breakdown due to heating.

5. A spark-plug construction comprising a grounded body including a barrel portion having a socket lined with insulation and opening through the upper end of the barrel portion to receive an ignition lead, means in the socket for connecting the lead with the plug, threads on the l5 sides of the barrel portion adjacent its upper end,

a metal elbow throughwhich the ignition lead passes immediately above the barrel portion, a connection between the metal elbow and said barrel portion including an externally ilanged end 20 member secured to the lower end of the metal elbow and 'resting on the upper end of the barrel portion, a coupling nut on the threads of the body portion, and a shoulder on said nut extending over the iiange on the end member of the elbow 25 to fasten the elbow to the body of the plug, said nut and end member being of metal and serving as conductors of heat from the barrel portion to the elbow to increase-the heat radiating surface of the spark plug, and means at the upper end of 30 said metal elbow for gripping the ignition lead to hold it agaimt being pulled out of the plug.

GEORGE M. PAULSON. 

